Abstract
Summary and conclusions
1. Continuing previous studies, employing improved bio-assay methods, the protective effect of cell-free saline extracts made from spleens of normal mice against X-ray-induced mortality in this species has been demonstrated. 2. Extracts made from the spleens of donor animals exposed to an X-ray dose which killed 55% of the donor animals in 14 days failed to show a protective effect, which was in agreement with previous observations. 3. A certain amount of parallelism between the protective effect of various extracts made from normal mouse spleens and the failure to protect of those made from irradiated mouse spleens was found in studies of the total protein and NPN content of such extracts. 4. It appears that within a wide range of concentration of total protein and NPN content such protection can be achieved. 5. However, reduction of average content of total protein and NPN below one-half of lowest average value for normal spleens, ascertained in samples made from spleens of irradiated donor animals, was found to be associated with a lack of protection. Whether this failure is due merely to quantitative or also to qualitative differences in these extracts is not clear.
Since the writing of this paper, an article by Allen et al. appeared in Science, 1956, v123, 1080, in which postirradiation protection of rabbits with plasma obtained from the splenic vein has been reported. Presence of a humoral spleen factor has thus been indicated in another animal species with a different method.
Technical assistance rendered by W. A. Sterling, R. L. Devault. R. Crutcher, and personnel of the Radiation Technology Division is acknowledged with thanks.
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